Field of the Invention
The present invention relates to an image pickup apparatus that drivingly controls lenses constituting an image pickup optical system and a control method therefor, and in particular to an image pickup apparatus that attains proper focus by correcting for variations in the shooting angle of view during a focusing operation and a control method therefor.
Description of the Related Art
Generally, in image pickup optical systems (lens barrels) of image pickup apparatuses such as photographic cameras and digital cameras, focusing is performed by moving a focus lens in a direction of an optical axis, and zooming is performed by moving a zoom lens in the direction of the optical axis. In recent years, due to widening and miniaturization of lenses, even when the distance to a subject does not change, the amount by which a focus lens group is extended so as to adjust focus in response to zooming, or the sensitivity of a focus lens to the angle of view associated with zooming is high. When the angle of view is caused to greatly change by focusing, there arises a problem that there is a wide divergence from an angle of view desired by a person who shoots, and it is impossible to take intended pictures (images).
As a way to solve this problem, there is known a technique that corrects the angle of view by driving a zoom lens in accordance with a focus lens when focusing. Here, in digital cameras, for example, the cell pitch of an image pickup device is becoming smaller due to an increase in the number of pixels of image pickup devices. The decrease in the cell pitch of the image pickup devices will make the allowable depth shallower and decrease the amount by which the focus lens and the zoom lens are driven. For this reason, drive characteristics of each lens affect focusing accuracy. Accordingly, for example, there has been proposed a technique to correct for a backlash of a focus lens based on a drive load on the focus lens when it is reversed (see Japanese Laid-Open Patent Publication (Kokai) No. 2013-80082).
The technique described in Japanese Laid-Open Patent Publication (Kokai) No. 2013-80082, however, has no technical concept that a focus lens and a zoom lens are driven at the same time. Thus, a new technique is required so as to obtain satisfactorily high focusing accuracy while suppressing variations in the angle of view during lens drive control that drives a focus lens and a zoom lens at the same time.